Semiconductor devices are used as amplifiers for high power microwave transmissions. These devices are part of base station and mobile systems of wireless networks used for telecommunications and metro communications. For example, a semiconductor device may be a Gallium nitride (GaN) transistor or a GaN Microwave Monolithic Integrated Circuit (MMIC) used as a high power amplifier. Recently, device power is increasing in high performance small size die. As such, more cost effective solutions are needed as these amplifiers increase in number and replace current amplifiers.
The heat-sink material must be chosen to have high thermal dissipation. It should also be suitable for volume manufacturing. In general, amplifiers and packages which are smaller in size and can be manufactured in volume tend to be more cost effective than larger ones which require a special metal heat-sink.
For the packaging of semiconductor devices, copper/tungsten (Cu/W) or copper/molybdenum (Cu/Mo) composites are frequently used in the fabrication of their heat-sinks. However, these heat-sink materials do not have enough thermal dissipation to manage the heat generated by high power semiconductor devices. Other materials used in heat sinks, for example, special composite materials with diamond or carbon powder, have been developed to manage good thermal conductivity. However, these special materials, especially those with diamond or other carbon components, tend to be very expensive. In addition, these materials may experience difficulties in the manufacturing process, such as having good yield during plating and brazing, which in turn affects their suitability for volume manufacturing.
The copper materials discussed above also have high thermal expansion, which does not match well to the coefficient of thermal expansion of a ceramic frame. The coefficient of thermal expansion difference between the copper materials and a ceramic frame is too great to manage the extremes of an environmental test. If the environmental test is not managed adequately, then the reliability of the semiconductor device and semiconductor package will be lower, and failure of the semiconductor device and semiconductor package may occur. Thus, there is a need for an improved semiconductor package.